1. Field of the Invention
The present invention generally relates to a method for recording and reproducing information on and from a disk-shaped recording medium having a spiral track such as an optical disk, and, more particularly, to a recording and reproducing method for an optical disk, in which the information is recorded and then reproduced on and from the recording portions except for defective portions present in the recording medium.
2. Description of the Prior Art
Conspicuous developments have been recently made in the optical information recording/reproducing device, for instance, video disks and digital audio disks. Demands for the electronic filing devices have also been required, wherein the image information such as large quantities of a document is optically scanned in the two-dimensional mode to be photoelectrically converted. The photoelectrically converted image information is recorded on the image recording device such as an optical disk, and can be retrieved to obtain the reproduced image information, depending upon the requirement.
In the typical recording/reproducing method for the optical recording/reproducing device, while the optical disk having a recording plane made of a photo sensitive recording material is rotated, the information signal is recorded at a high density on the recording plane by the way of formations of concaves/convexes, or holes, changing the reflectivity, or the magnetizing direction, by irradiating an optical light spot such as a laser on the optical disk after focusing the laser light to produce the optical light spot having a diameter of approximately 1 .mu.m (micrometer). Moreover, the information signal recorded on the optical disk is reproduced from the recording plane. In the optical disk device where the information is recorded in the spiral form, recording, or reproducing the information on the optical disk is performed by the optical head which is linearly moved in the radial direction of the optical head by employing the linear motor.
An optically detectable guide track is formed on a optical disk with the narrow track pitch so as to record the information at a high density. This guide track is selected in accordance with the contents of the information to be recorded, or the types of the signals to be recorded. In general, a guide track is formed in a spiral form, or a concentrical form with respect to a center of an optical disk. When the information to be recorded corresponds to an analogue mode, the guide track is normally supervised in the track unit. When, on the other hand, the information to be recorded is in a digital mode, such track-unit supervision becomes inconvenient because the length of the information is not decided which is different from the track unit supervision for the video signal. Accordingly, the information to be recorded is supervised with the track address and sector address by dividing each track into a plurality of information regions, which are so-called "sectors".
As a method of forming the guide track, the pregroup forming method has been usually employed where the guide track is formed in a groove form, and simultaneously both the track address and the sector address are formed in a concave-convex phase groove. In addition, the preformating method has been utilized where the refractive index of the photo-sensitive recording material is changed by employing a high power optical source prior to the information recording on the flat recording plane, and the guide track, track address and sector address are formed by changing the refractive index.
It is known that an optical disk has the merit of recording large quantities of information a higher density, but has the drawback that there are many defective regions where the data cannot be correctly recorded due to scratches or soil. As a result, the reliability on the data recording will be degraded since the data may be recorded on the defective regions of the optical disk.
Japanese patent KOKAI (unexamined) application No. 60-69865 (1985) discloses one solution for solving the above-described drawback of the conventional data recording method. That is to say, in accordance with the detection results of the detecting means for detecting the defect of the data block, the defect-block-data-address data representing the defect block is recorded on the predetermined recording area of the optical disk, while the information is recorded on the block other than the above-described defect block.
As another prior art solution for the recording and reproducing problems, Japanese patent KOKAI (unexamined) application No. 60-109034 discloses that in order to avoid the error operations in the defect areas, the sectors containing the defects are previously detected to produce the detection information which is stored in the memory of the disk controller, the optical spot passing through the sectors containing the defects is previously detected based upon the above-described information stored in the memory, and the recording and reproducing operations are performed by passing the optical spot through the other track adjacent to the track belonging to the above-described defective sector during a period of time substantially coincident with a time duration in which this optical spot passes through the sector containing the defects.
In general, the above-defined recording processes where the data recording is performed by preventing the data from being recorded on the defective regions, are mainly subdivided into the precheck system and the verify system. In accordance with the precheck system, prior to the information recording operation, the defective sector on the disk is prechecked, and then the information is recorded on only the non-defective sector while skipping the optical spot on the defective sector during the recording operation.
On the other hand, in the verify system, several sectors in the end portion of one track on one circle of the optical disk are allocated as the preliminary area, whereas the remaining portion of one track is allocated as the user's area. First, the information is recorded on the user's area. Thereafter, a check is made by reproducing the user's area to determine whether or not the information has been correctly recorded on the user's area. Then, the information erroneously recorded on the user's area of the sector is recorded on the above-described preliminary area. Finally the check is made by reproducing the preliminary area to determine whether or not the information is correctly recorded on the preliminary area.
In accordance with the above precheck system, even if the precheck results were correct, the information may not be correctly recorded when the information is actually recorded and thereafter reproduced. This precheck method results in poor reliability.
In the verify system, a time consuming problem may be present to accomplish the information recording process. That is to say, the information is recorded on the user's area of one track during the first rotation of the optical disk. Thereafter, the error detection is performed by reproducing the information just recorded on this user's area. However, no reproducing operation is effected during the second rotation since the head (i.e., optical pick up) cannot seek the track head of this track within a shorter time period during which the disk is rotated by an angle of .theta. (corresponding to the preliminary area) from the end point of the recording operation. In other words, the head seeking operation is completed during this second rotation. The user's area is reproduced during the third rotation of the optical disk so as to check the errors thereon. When the errors are detected, the information belonging to the error recording operation is recorded on the preliminary area located at the end portion of the same track during the third rotation. Subsequently, the head again seeks the track during the front half of the fourth rotation and reproduces the preliminary area to determine whether or not the error is present therein. No further description is made herein when the recording errors are present in the preliminary area.
As previously described in detail, the substantial time period, i.e., three rotations required even if no error is present in the recorded data. Moreover, a longer time period for four rotations is required when an error is detected from the recorded data (it should be noted that the time period required for rotating the optical disk during the five rotations in total is furthermore needed, taking account of the fact that one additional disk rotation is required so as to change the information recording process from the reproducing and error-detecting process during the fourth rotation to the succeeding track process). This causes the through-put to be lowered.
Another theme is addressing systems for acquiring the necessary information as quickly as possible with respect to the information recording of the optical disk.
In accordance with one conventional addressing method, the number of the sectors on which the information has been recorded is counted from the head portion of the optical disk, and the information recorded on the i-th sector is reproduced so as to obtain the necessary information (in the sector unit) which has been recorded in the i-th order.
In the second conventional addressing method, the information representing where the defective sectors are present in the optical disk is stored in the system. When the i-th recorded information (i.e., the information of the logic address) is acquired from this optical disk, it can be understood that the information "i" has been recorded on the specific sector of the specific track (i.e., the physical address of the optical disk) by referring to the positional information of the above-described defective sector. Accordingly, this information can be directly accessed.
A very lengthy time period is required to acquire the necessary information when employing the first addressing method. Since the number of the recorded sectors must be counted from the head track portion of the optical disk, the counting time becomes considerably long so as to acquire the necessary information recorded on the rear track position of the optical disk.
In accordance with the second addressing method by which the positional information representing the defective sectors is stored in the system, the necessary information can be quickly acquired. This addressing method may be preferably utilized in an apparatus where the recording medium is fixedly assembled with respect to the system, such as the fixed disk devices. However, this second addressing method is not a realistic method, since all the information representing the defective positions for all of the disks must be supervised by the respective optical disk devices. In such optical disk devices, a large number of the optical disks are freely set on a large number of the optical devices at random.